Veterinary Medicine - October 2008 - (Page 557)

transport of uric acid into the liver and to have increased excretion of uric acid into the urine. All Dalmatians appear to have these alterations in uric acid metabolism, but only a small percentage actually develop urate uroliths. The Dalmatians developing these uroliths are most commonly affected at 1 to 4 years of age, with a decrease in incidence after 6 years of age.14,24 Although the cause of the English bulldog’s predisposition to urate urolith formation is not clearly de ned, it has been theorized that a renal proximal tubular defect and alterations in purine liver metabolism cause increased urate urolith formation in this breed.38 Dogs other than Dalmatians and bulldogs and some cats can be at risk for developing urate uroliths because of changes in metabolism related to hepatic disease, especially portovascular anomalies, including hepatic microvascular dysplasia.39 Miniature schnauzers, Yorkshire terriers, and Shih Tzus are at increased risk.24 Urate uroliths can be found in both male and female dogs with portovascular anomalies and are commonly diagnosed when the patient is < 3 years old.39 In many cats, urate urolith formation is idiopathic but may occur as a result of portovascular anomalies.25,34 No known sex or breed predisposition has been established for cats.34 Although urate uroliths occur most commonly in cats that are < 4 years old, urate uroliths associated with portovascular anomalies are frequently found in cats < 1 year of age.34 because of carnitine de ciency.14,24 The time required for urolith dissolution averages about three or four months. It may be necessary to add allopurinol (15 mg/kg orally twice a day), a competitive inhibitor of the enzyme xanthine oxidase, to the dissolution protocol.39 In cats, allopurinol (7.5 mg/kg orally twice a day) and Prescription Diet Feline k/d (Hill’s Pet Nutrition) can be used in a dissolution protocol.30 Administering allopurinol to treat or prevent urate uroliths may result in xanthine urolith formation because allopurinol inhibits xanthine oxidase. Therefore, always feed a purine-restricted diet (e.g. Prescription Diet Canine u/d, Prescription Diet Feline k/d) to patients receiving allopurinol. Urate uroliths in cats and urate uroliths associated with portosystemic shunts often cannot be medically dissolved.13 Consequently, voiding urohydropropulsion, lithotripsy, or surgical intervention is often required to remove urate uroliths in these patients. Spontaneous dissolution of urate uroliths after correcting portovascular anomalies may occur but has not been documented with published studies.24 Urinary tract infections occur commonly with urate Treatment. In dogs, urate uroliths can be medically dissolved either completely or partially in about two-thirds of the cases in which an appropriate calculolytic diet is given.14,24 The calculolytic diet of choice for dogs is Prescription Diet u/d, which is low in dietary purines, alkalinizes urine, and forms a more dilute urine. Because of nutrient restrictions, Prescription Diet u/d should not be given to pregnant or lactating bitches or immature dogs and should be given with caution to English bulldogs, which may develop dilated cardiomyopathy http://www.arbex.com http://www.arbex.com

Table of Contents Feed for the Digital Edition of Veterinary Medicine - October 2008

Veterinary Medicine - October 2008 Contents Leading Off Clinical Exposures Idea Exchange Stalking Stones Vaginitis in Dogs CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - October 2008

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